MCP Server Malcolm

Malcolm MCP Server

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Malcolm MCP Server lets an AI agent ask questions about the traffic in your Malcolm instance. The server uses the field names and the filter syntax that Malcolm uses. The agent does not guess them. It works with any MCP client, such as Claude Code, Claude Desktop or Cursor.

Example requests, and the tools that answer them:

• "Show every Suricata alert involving 192.0.2.15 in the last 24 hours, and which NetBox device owns that IP." This calls malcolm_alerts and malcolm_netbox_lookup.
• "Who were the top talkers by protocol over the last hour?" This calls malcolm_aggregate.
• "List the executables Zeek carved out of yesterday's traffic, with their hashes." This calls malcolm_file_scans.
• "Upload this PCAP, then hunt the stored packets for this string." This calls malcolm_upload_pcap and arkime_create_hunt. Both are write tools, and they are off by default.

A recorded session shows an agent answering a question about Modbus alerts.

Requirements

• Python 3.11 or newer.
• A Malcolm instance with API access, reachable over HTTPS.
• An MCP client.

Quick start

1. Install the server. Then start it with stdin closed. It prints the state of the write classes and exits with code 0.

pip install mcp-server-malcolm

mcp-server-malcolm < /dev/null

[mcp-server-malcolm] write classes: alerting=off arkime-tag=off hunt-job=off pcap-upload=off arkime-view=off

2. Register it with Claude Code. Replace the values with your own.

claude mcp add malcolm \

-e MALCOLM_URL=https://malcolm.example \ -e MALCOLM_USERNAME=analyst \ -e MALCOLM_PASSWORD='your-password' \ -e MALCOLM_SSL_VERIFY=/path/to/malcolm-ca.crt \ -- mcp-server-malcolm

Everything after -- is the launch command. Each -e sets one environment variable for it. A password typed in this command stays in your shell history. The install page shows how to avoid that. It also covers other MCP clients and other ways to install.

3. Check the connection. Ask the agent to call malcolm_ping. If the call fails, read Troubleshooting. A self-signed certificate is the most common cause.

Connection settings

Malcolm ships a self-signed certificate. For a remote Malcolm, point MALCOLM_SSL_VERIFY at the CA bundle. The certificate must carry a subjectAltName that matches the host name. The certificate that Malcolm's own setup generates has none, so install one that does. Use false only on an isolated lab machine. The configuration page lists every variable.

Read-only by default

The write tools come in five classes, and each class has one flag. The server registers only read tools until you set a flag. A class that is off is not registered. Its tools do not appear in tools/list.

A flag is on only when its value is true. Every write attempt writes one audit line, to stderr or to the file in MALCOLM_MCP_AUDIT_FILE. The security page describes the model.

Tools

The server has 51 read tools. They cover Malcolm filter queries, aggregation, field lookup, Arkime sessions and packets, NetBox, Zeek file scans, saved objects and alerting monitors. The tools page lists them all.

The tool schemas use about 34,000 tokens in every session. To save tokens, set MALCOLM_MCP_DISABLE_READ_GROUPS to the groups you do not need. For example, netbox,dashboards,detections,arkime-inventory leaves 34 tools. See Trimming the read surface.

Non-goals

Version 1 leaves these out on purpose:

• Destructive writes (Arkime session delete, tag removal, user management).
• Raw OpenSearch write or raw NetBox CRUD passthrough, behind a flag or otherwise.
• The streamable-http transport (stdio only).

Repository structure

├── src/mcp_server_malcolm/    # The server

│ ├── server.py # Registers the tools, applies the write gate │ ├── client.py # HTTP client for Malcolm │ ├── config.py # Write-class flags │ ├── audit.py # Audit output │ └── tools/ # Read tools. Write tools are in write/ ├── tests/ # Tests ├── scripts/ │ └── api_parity_check.py # Compares each tool with the Malcolm API ├── docs/ │ ├── install.md # Install, register, other install routes │ ├── container.md # Run in a container │ ├── configuration.md # Connection settings, every variable │ ├── troubleshooting.md # The first call fails │ ├── tools.md # Read tools, write tools, trimming │ ├── security.md # Security model, audit │ ├── usage.md # Demo, filter syntax, examples │ ├── python.md # Use the client from Python │ ├── design.md # Why an MCP layer, protocol notes │ ├── verification.md # Parity check, tested platforms, API endpoints │ └── zh-TW/ # Copy of these pages for README.zh-TW.md ├── Dockerfile # Container image ├── server.json # MCP Registry manifest ├── SECURITY.md # Report a vulnerability ├── CONTRIBUTING.md # How to contribute └── CHANGELOG.md # Changes per version

Development

pip install -e . pytest pytest-asyncio ruff

ruff check src tests ruff format --check src tests pytest

The tests do not need a Malcolm instance. See CONTRIBUTING.md.

License

MIT